Journals
Authors:
Beamurgia Bengoa, M. (Corresponding author); Basagoiti, R.; Rodríguez, Ignacio; et al.
Magazine:
SOFT COMPUTING
ISSN:
1432-7643
Year:
2022
Vol:
26
N°:
24
Pp:
13673 - 13692
Passenger waiting time is a significant issue related to the quality of service of a multiple lift system; however, energy consumption reduction is also an important concern in the lift industry. In this paper, we evaluate different versions of a genetic algorithm (GA) published previously by the authors with several relevant adjustments for the lift dispatching problem to minimize passenger waiting time and/or energy consumption. To the raw GA with adjustments (that works under the assumption one call-one passenger), we incorporated several elements: a passenger-counting module using origin-destination matrices, and the activation of certain policies (zoning and/or parking) under different detected traffic profiles (up-peak, interfloor or down-peak profiles). Besides, we added a proportional integral controller (PI) to assign different weights to passenger waiting time and energy consumption to evaluate the performance of our GA. Different versions of this GA, minimizing passenger waiting time and/or energy consumption, were compared among them and to a conventional control algorithm using three different types of simulated profiles: a mixed one, three well-known full day office profiles and three different step profiles. The results showed that the bi-objective GA version with the estimation of the number of passengers behind a call, i.e. the passenger forecasting, together with the parking policy for up-peak or down-peak conditions significant
Magazine:
JOURNAL OF MODELLING IN MANAGEMENT
ISSN:
1746-5664
Year:
2021
Vol:
16
N°:
2
Pp:
464 - 485
Purpose This study aims to reduce carbon emissions and costs in an automobile production plant by improving the operational management efficiency of a serial assembly line assisted by a feeding electric tow vehicle (ETV). Design/methodology/approach A multi-objective function is formulated to minimize the energy consumption of the ETV from which emissions and costs are measured. First, a mixed-integer linear programming model is used to solve the feeding problem for different sizes of the assembly line. Second, a bi-objective optimization (HBOO) model is used to simultaneously minimize the most eco-efficient objectives: the number of completed runs (tours) by the ETV along the assembly line, and the number of visits (stops) made by the ETV to deliver kits of components to workstations. Findings The most eco-efficient strategy is always the bi-objective optimal solution regardless of the size of the assembly line, whereas, for single objectives, the optimisation strategy differs depending on the size of the assembly line. Research limitations/implications Instances of the problem are randomly generated to reproduce real conditions of a particular automotive factory according to a previous case study. The optimization procedure allows managers to assess real scenarios improving the assembly line eco-efficiency. These results promote the implementation of automated control of feeding processes in green manufacturing. Originality/value The HBOO-model assesses the assembly line performance with a view to reducing the environmental impact effectively and contributes to reducing the existent gap in the literature. The optimisation results define key strategies for manufacturing industries eager to integrate battery-operated motors or to address inefficient traffic of automated transport to curb the carbon footprint.
Magazine:
HEALTH CARE MANAG SC
ISSN:
1386-9620
Year:
2020
Vol:
23
N°:
1
Pp:
66 - 79
We study the efficiency of operations management in a hospital from the dynamics of the flow of patients. Our principal aim is to characterize strategic departments and seasonal patterns in a hospital from a complex networks approach. Process mining techniques are developed to track out-patients¿ pathways along different departments for the purpose of building weekly networks. In these networks, departments act as nodes with multiple out/in-going arrows connecting other departments. Strategic departments are classified into target and critical departments. On the one hand, target departments, which in this study belong to the oncology area, correspond to those affected by new management policies whose impact is to be assessed. On the other hand, critical departments correspond to the most active departments, the hubs of the networks. Using suitable networks parameters, strategic departments are shown to be highly efficient regardless of the season, which naturally translates into a high level of service offered to patients. In addition, our results show conformance with the new objectives concerning target departments. The methodology presented is shown to be successful in evaluating the efficiency of hospital services in order to enhance process performances, and moreover, it is suitable to be implemented in healthcare management systems at a greater scale and the service industry whenever the flow of clients or customers are involved.
Magazine:
ENVIRONMENTAL QUALITY MANAGEMENT
ISSN:
1088-1913
Year:
2018
Vol:
27
N°:
3
Pp:
135 - 146
Global warming is negatively affecting the environment of the planet. This situation has led to the development of international standards, such as the International Organisation for Standardization's DIS 14064-1 and the Greenhouse Gas Protocol Corporate Standard, both of which measure corporate carbon footprints. These standards provide guidelines that can be applied to different organisational sectors. However, these are not sufficient for controlling the reduction of carbon emissions, because although they propose the use of indicators, they do not explicitly define them. In addition, in the case of emissions from wastewater treatment, they only suggest that the emissions associated with this process be considered. In the present study, an eight¿step, unified methodology based on these two international standards is proposed, focusing on direct emissions. Moreover, the step-by-step approach to data collection, calculations, and the required indicators to control the emissions are defined. The first scope considers direct emissions from sources that are owned or controlled by the company. Methane generation measurement from wastewater treatment has been included in the methodology within Scope 1, as it is the second most polluting gas after carbon dioxide, both of which give rise to global warming. The proposed methodology was tested as a case study in one of the most important companies in the food sector in Colombia.
Magazine:
SOFT COMPUTING
ISSN:
1432-7643
Year:
2016
Vol:
20
N°:
9
Pp:
3595 - 3609
Reduction of passenger waiting time in a multiple elevator system is an important goal in the lift industry. Genetic algorithms (GAs) have been applied to the dispatching problem in vertical transportation. In this paper, we present an approach based on a GA with several relevant adjustments to adapt this type of algorithm to this problem. The algorithm serves calls currently registered in the system to create a dispatch plan, under the assumption that just one passenger has made each call (i.e. without passenger forecasting). We develop and investigate various versions of the GA incorporating one or more adjustments in this research area. The algorithms were implemented and evaluated using ELEVATE, for two different building configurations, in terms of incoming, outgoing and interfloor profiles. To compare results, one-factor analysis of variance tests were applied to passenger waiting times. The performance of the basic GA was significantly improved upon by making these adjustments. These adjustments turn out to be essential for a successful implementation of a GA in the dispatching problem.
Magazine:
INTERNATIONAL JOURNAL OF PRODUCTION RESEARCH
ISSN:
0020-7543
Year:
2016
Vol:
54
N°:
3
Pgs:
878 - 893
The Assembly Line Part Feeding Problem (ALPFP) is a complex combinatorial optimisation problem concerned with the delivery of the required parts to the assembly workstations in the right quantities at the right time. Solving the ALPFP includes simultaneously solving two sub-problems, namely tour scheduling and tow-train loading. In this article, we first define the problem and formulate it as a multi-objective mixed-integer linear programming model. Then, we carry out a complexity analysis, proving the ALPFP to be NP-complete. A modified particle swarm optimisation (MPSO) algorithm incorporating mutation as part of the position updating scheme is subsequently proposed. The MPSO is capable of finding very good solutions with small time requirements. Computational results are reported, demonstrating the efficiency and effectiveness of the proposed MPSO.
Magazine:
EUROPEAN JOURNAL OF INDUSTRIAL ENGINEERING
ISSN:
1751-5254
Year:
2016
Vol:
10
N°:
2
Pp:
145 - 169
The U-shaped assembly line has received considerable attention and has been widely used in industry in recent years due to the pressures of the just-in-time (JIT) manufacturing philosophy. However, balancing the U-shaped line is more difficult than balancing the traditional straight line. This study aims at balancing the U-shaped assembly line by introducing a novel heuristic which is based on the simulated annealing (SA) algorithm. The objectives to be optimised in this study are the number of workstations and balance efficiency. The performance of the proposed algorithm is examined by solving a set of standard test problems and a real case study. The results attained by the proposed algorithm were compared against the best known solution in the literature and it was found that the proposed algorithm is able to find good solutions in a reasonably short computational time.
Magazine:
MATHEMATICAL PROBLEMS IN ENGINEERING
ISSN:
1024-123X
Different aspects of assembly line optimisation have been extensively studied. Part feeding at assembly lines, however, is quite an undeveloped area of research. This study focuses on the optimization of part feeding at mixed-model assembly lines with respect to the Just-In-Time principle motivated by a real situation encountered at one of the major automobile assembly plants in Spain. The study presents a mixed integer linear programming model and a novel simulated annealing algorithm-based heuristic to pave the way for the minimization of the number of tours as well as inventory level. In order to evaluate the performance of the algorithm proposed and validate the mathematical model, a set of generated test problems and two real-life instances are solved. The solutions found by both the mathematical model and proposed algorithm are compared in terms of minimizing the number of tours and inventory levels, as well as a performance measure called workload variation. The results show that although the exact mathematical model had computational difficulty solving the problems, the proposed algorithm provides good solutions in a short computational time.
Magazine:
INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY
ISSN:
0268-3768
Year:
2014
Vol:
75
N°:
1
Pp:
629 - 643
In recent years, part feeding at assembly lines has become a critical issue as the result of a high level of product customisation. The assembly line part feeding problem is a complex problem in which a number of decisions should be made in order to select the right quantity of each part to be supplied at the right time under a set of constraints. This study aims to cope with the part feeding problem at assembly lines by introducing a new memetic ant colony optimization-based heuristic algorithm. Due to the novelty of the problem and in order to evaluate the performance of the proposed memetic algorithm, a mathematical formulation is also presented. Case data from an automobile manufacturer and a set of generated instances are used to test both the mathematical model and the proposed memetic algorithm. The results reveal that although it is computationally difficult to solve the problem using the exact mathematical model, the mimetic algorithm was able to find sufficiently good solutions in a short period of time.
Magazine:
EDUCADE
ISSN:
2173-478X
Year:
2014
Vol:
5
Pgs:
19 - 31
Magazine:
PROCEDIA: SOCIAL & BEHAVIORAL SCIENCES
ISSN:
1877-0428
Year:
2012
Vol:
47
Pgs:
1616 - 1621
This study considers the effect of the usage of a social network site (www.grouply.com) for a class related group project on the development of individual abilities and performance in group work. Data were collected from three sections of an intermediate macroeconomic class at a Spanish university and groups were randomly assigned to work (or not) using the social network. Findings suggest that, although students are in general attracted by the idea of using SNS in class-related team work, the introduction of a tool they are not familiar with may hamper their self-perceived level of competence in a number of skills.
Magazine:
WORLD ACADEMY OF SCIENCE, ENGINEERING AND TECHNOLOGY. PROCEEDINGS
ISSN:
1307-6884
Year:
2011
Vol:
59
Ppgs:
413 - 421
Magazine:
ALIMENTARIA
ISSN:
0300-5755
Year:
2011
N°:
423
Pp:
72 - 80
Magazine:
TECNURA
ISSN:
0123-921X
Year:
2011
Vol:
15
N°:
30
Pp:
71 - 81
Breaks in the cold chain represent important economic losses in pharmaceutical and food companies. Many of the failures in the cold chain are due to inadequate adjustment of equipment parameters, such as setting parameters for theoretical conditions without corresponding verification under normal operating conditions. Companies transporting refrigerated products must be able to adjust equipment parameters easily and quickly to adapt their operation to changing environmental conditions. This article presents the results of a study carried out with a food distribution company business . The main goal of the study is to verify the effectiveness of the "Six Sigma" methodology as a methodological tool to adjust the parameters of the equipment in the cold chain. The second goal is more specific and consists of studying the impact of: the reduction of the storage volume in the truck, the initial temperature of the storage area in the truck and the frequency of defrosting in the transport of refrigerated products.
Magazine:
INTANGIBLE CAPITAL
ISSN:
1697-9818
Year:
2010
Vol:
6
N°:
2
Pp:
202 - 235
Magazine:
TRANSPORTATION RESEARCH PART E-LOGISTICS AND TRANSPORTATION REVIEW
ISSN:
1366-5545
Year:
2010
Vol:
46
N°:
3
Pp:
367 - 383
One of the most important challenges that confronts less-than-truckload carriers serving many-to-many distribution networks consists of determining how to consolidate flows of small shipments. The objective is to determine a route for each origin-destination pair that minimizes the cost while still guaranteeing a certain level of service. This research studies different aspects of the problem and provides a metaheuristic algorithm (based on Ant Colony Optimization techniques) capable of solving real-life problems in a reasonable computational time. The viability of the approach has been tested with a real case in Spain and encouraging results have been obtained.
